The Finnish patent No. 56.552 describes a procedure for producing starch from barley, in which the whole barley grains are steeped in water warmed to 40.degree.-55.degree. C., and containing 0.3% sulphur dioxide for 5-48 hours. The steeped grains are ground with process water so that the hull parts are left relatively intact and the endospermic part of the grains is comminuted into particles less than 0.1 mm in size. The ground barley is sifted with water and the starch is separated from the filtrate using the difference in sedimentation rate. The heavy starch fraction is washed and concentrated by a plurality of steps based on the difference in sedimentation rates.
In this process different fractions of products are obtained in the several different steps. The grains are separated to a starch fraction, a protein fraction, and a fibre fraction. Normally all products are dried to increase storage stability. This is accomplished by various types of dryers, or soluble fractions are dried by evaporators.
Several methods and agents have been used to improve the separation process, for example, pH adjustment or heat coagulation of proteins from process water.
U.S. Pat. No. 4,428,967 discloses a process for the production from barley of a maltose syrup as main product, comprising adding to barley flour and enzyme containing beta-glucanase and preferably also alpha-amylase. Beta-glucanase is added to partially hydrolyze the beta-glucans present and to reduce the viscosity to workable levels. The optional addition of alpha-amylase serves to initiate the hydrolysis of starch. This process provides starch of a relatively inferior quality, which is used as intermediate for the production of maltose syrup.